The goals of this proposal are to elucidate the function of two novel mammalian genes. The first of these is SNM1, a mammalian homologue of the yeast DNA repair gene. This gene is a member of the rad3 epistasis group and is known to be specifically involved in the repair of lesions produced by interstrand crosslinking agents. Evidence from studies in yeast suggests that the expression product of this gene functions in the later stages of crosslink repair to effect reconstitution of high molecular weight DNA. The second gene is most closely related to the lodestar gene of Drosophila. Studies of this gene in Drosophila suggest that it is a mitotic factor involved in the segregation of chromosomes during anaphase. The exact function of lodestar is not clear, and has been postulated to be involved in a number of processes including chromosomal condensation, DNA repair, or dissolution of the factors that maintain sister chromatid cohesion, such as DNA intertwining or protein-protein interactions. We plan to analyze the function of these genes in mammalian cells by a variety of methods. These include protein expression and localization as a function of the cell cycle, protein-protein interactions with either novel or known factors, and disruption of function through several approaches including antisense expression, conversion by chimeric oligonucleotides, and construction of homozygous -/- knockout mice.